ITEM: U8695L

Tctl command not working on 9-track tape drive (model 9348)

  AIX 3.2.5
  Model 9348 9 track tape drive.

  Attempting to retension old tapes, to ensure continued
  usage, using tctl retension command and nothing appears to


The 9348 tape drive is an IBM supported tape drive.  The reason the
retension doesn't work on this is because the drive doesn't HAVE to
retension the tape (therefore it doesn't).  Only the 1/4" technology
drives actually do a retension.  For education purposes, the reason a
tape needs retensioning is because, within a cartridge, it may
naturally become loose through motion or shaking such that it rides
loosely over the heads.  Thus a potential problem of binding or error
exists.  This is true for 1/4" technology.  Now, for 8MM and 4MM DAT
tapes, the tape is wound around a read/write head and tension is
maintained by tensioner arms.  Thus, no matter how loose the tape may
be in the cartridge, the tape drive itself maintains proper tension
around the head.  No need for a retension then.  This is obviously a
more sophisticated technology.  Now when we get to 9-track tape
drives, this is a MUCH MORE sophisticated technology.  It also has
tensioner arms to maintain a constant tension or the tape over the
read/write heads.  Thus, no need to retension the tape.  Now for
drives that don't need to retension the tape, the device driver, when
it see the retension command, will return the tape to the load point
(rewind it).  If the tape is already rewound, then it appears as if
nothing happens.  THAT is the reason for what the customer is seeing.
So everything is OK.

  Closing call.

Support Line: Tctl command not working on 9-track tape drive (model 9348) ITEM: U8695L
Dated: May 1995 Category: N/A
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